Human bone consists of hard outer cortex and a soft medullary cavity containing bone marrow. Marrow consists of stroma or the supporting tissues and its spaces packed by blood cells. Blood cells are manufactures in the bone marrow and are released in the peripheral blood. Therefore it is logical to look at a specimen of marrow to diagnose diseases of blood cells such as leukemias. Traditionally, marrow was obtained by aspiration method using a large bore needle like device and a syringe. Entering the marrow cavity with the needle and aspirating with the syringe causes negative pressure sufficient to break delicate marrow stroma and release of fluid marrow to be aspirated in the syringe. However, this aspiration sample was not sufficient to diagnose some non-blood cell diseases affecting the marrow. For example, marrow forms a very convenient nidus for cancer cells coming from other organs. Aspiration procedure was not sufficent to disloge these cells from the stroma of the marrow. Hence, to diagnose cancers in the bone marrow such as lymphomas and other metastatic cancers it was necessary to obtain intact marrow in solid form. The procedure to obtain a solid sample of marrow is called marrows biopsy. Traditionally, a solid core of marrow biopsy was obtained by pushing a larger bore needle with hollow lumen into marrow cavity. As the needle is pushed, a core of marrow enters the lumen. The needle containing the marrow is withdrawn and the core expressed out using a blunt probe. Current art includes designs that one can aspirate or biopsy the marrow using the same needle but it still requires two separate procedures requiring to penetrate the bone marrow twice albeit close to each other. This means two painful procedures for the patient and sometimes more frequently, depending on the success of the procedure each time.
It should be realised one cannot perform aspiration or biopsy from any bone of the body. A traditional method of obtaining a fluid aspirate of marrow was from the sternum which is a chest bone in the front. The needle used for this purpose is short because sternum is a flat and thin bone and longer needles may penetrate the bone completely and injure vital structures underneath. One should never attempt a biopsy from the sternum even with a shorter needle. There have been inventions disclosed for biopsy of sternum before but those experienced in the field will know not to biopsy the sternum.
Obtaining aspiration and biopsy specimens from a large hip bone is the most popular method due to its safety. However, obtaining marrow specimen from the hip bone, the iliac crest, needs much larger and stronger needle. Considerable force is needed to pierce the bone. To overcome these difficulties, needles have been designed with improved cutting edges and various types of handle to give the operator grip to exert force. Needles with various shapes at their tip are available to get the biopsy without distortion and retaining it within the lumen of the needle while withdrawing. All the available needles however have not overcome the need to reduce the number of procedures less than two to obtain both biopsy and aspiration.
A successful biopsy requires, first, the force with which the needle can penetrate the thick and hard bony cortex. Second, the grip with which the operator can hold the needle in position. Third, the forward force with which the needle can be pushed in the bone. Existing needles do not fulfill these requirements and improvements are still being sought after and still being proposed.